When To Stop Optimizing, Or Even Improving A Page?

A particular page on my site has ranked #1 across the major SEs for years and this year I was unseated by an article by one of the 'big boys' (ESPN). My article was somewhat dated, so I went back and re-worked the content and made it much better, no result.

Their article on the subject isn't nearly as in-depth or complete as mine, but they are destroying me on the social side with shares and tweets. Since I am a small site I don't have the traffic to compare with those social numbers.

How do you determine at what point further optimization (or even further improvement of the content) is futile? I'd love to regain my spot back, but if the social factor is too large to overcome then it's probably wasted time.